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New Scientist Live

Frozen rabbit kidneys could solve organ shortage for transplants

Organs at the ready

Nicole Bengiveno/The New York Times/Redux/Eyevine

By Helen Thomson

IS THIS the coolest solution to our organ shortage? Researchers have discovered a way of freezing embryonic animal kidneys so that they can later be warmed up and grown into organs without the risk of rejection by their recipient.

In 2014, 17,000 kidney transplants were carried out in the US, but five times more people were on the waiting list. There are three challenges for human organ transplantation: the number of organs available, rejection of the organ by the host’s immune system, and timing – human kidneys can be kept alive for 30 hours at most outside the body.

This leaves us with too few kidneys available for transplant.Now Francisco Marco-Jiménez at the Polytechnic University of Valencia, Spain, and his colleagues have found a source of kidneys that don’t seem to cause immune rejection when transplanted between rabbits, and that can be stored for several months while awaiting transplantation.

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The team found that when precursor kidney tissue from 16-day-old rabbit embryos is implanted in adult rabbits, it develops into an adult kidney, connecting itself to the host’s blood supply. “The host doesn’t recognise the organ as strange, and permits it to connect to the blood system,” says Marco-Jiménez.

“The host doesn’t recognise the organ as strange, and permits it to connect to the blood system“

The adult rabbits did not reject the foreign kidneys because the embryonic tissue was transplanted before it had started producing the protein that would alert a host’s immune system to foreign cells. Marco-Jiménez believes that when the protein is eventually produced, it matches that of the host instead.

The team then investigated whether the tissue could be stored to create a transplant biobank. Large organs cannot be frozen to prevent decay because water in them turns to ice in the process, and this destroys cell structures.

But because the embryonic precursor kidneys are much smaller, the team was able to successfully use a cryopreservation process called vitrification, which pumps antifreeze into an organ before cooling it to -196 °C. This technique is normally only used to freeze small tissues such as human eggs because it is difficult to get the antifreeze around larger, more complicated organs.

The team then stored the precursor kidneys for three months in liquid nitrogen, before warming the tissue and transplanting it into adult rabbits (Cryobiology, doi.org/bdkm).

Some 25 per cent of the transplants grew into healthy adult organs in the host – not as high as the 50 per cent success rate they achieved with fresh embryonic tissue, but still promising.

“This work is, to my knowledge, the first to demonstrate successful vitrification of kidney precursors with recovery of biological function,” says Joao Pedro de Magalhaes at the University of Liverpool, UK. “This would have a lot of advantages in storing and distributing products for regenerative medicine.”

This article appeared in print under the headline “Frozen rabbit kidneys could solve shortage”